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Microwaves, Antennas and Propagation, IEE Proceedings H

Issue 6 • Date Dec 1988

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Displaying Results 1 - 14 of 14
  • Adaptive antenna array under directional and spatial derivative constraints

    Publication Year: 1988 , Page(s): 414 - 419
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    The author examines the beampattern dependency on the choice of phase centre location, when a narrow band beamformer is subjected to directional and spatial derivative constraints. He then presents a technique based on a power response approach, for deriving a new set of constraints for controlling the beampattern spatial derivates. The new set of constraints ensure that the array beampattern is independent of the choice of the phase centre co-ordinate origin. It is shown that for the first-order case, the constraint is linear, but for the second-order case, the constraint is quadratic. The author then presents a technique for approximating the effect of the quadratic constraint by two linear constraints. Finally, he presents a technique for optimising the beampattern with respect to the choice of the phase centre location, when the quadratic constraint is being approximated with linear constraints. View full abstract»

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  • Cylindrical waveguide mode convertor for azimuthally symmetric transverse electric modes

    Publication Year: 1988 , Page(s): 420 - 425
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    The propagation of the guided modes in a cylindrical waveguide with imperfectly conducting walls and with the radius having a weak harmonic variation in the axial direction is investigated using the expansion of the fields in terms of the ideal normal modes. The theory is applied to the design of a mode convertor that selectively transforms the power in the TE0r mode to the TE0s mode. The spectral response of the mode convertor is analysed and the possible improvements of the basic design of the mode convertor are discussed. View full abstract»

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  • Matching network characterisation by S-parameter measurements of two-part active devices

    Publication Year: 1988 , Page(s): 426 - 430
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (316 KB)  

    A method for characterising two-port matching networks at the input and output ports of a GaAs MESFET at a single frequency is described. Two steps are involved. First, measurement of the input reflection coefficient of the overall circuit with the transistor drain voltage equal to zero and for different values of the gate voltage. Secondly, S-parameter measurements of the overall circuit for two sets of transistor drain and gate bias voltages. Equations are presented which make possible the calculation of S-parameters of the passive matching networks from these measurements, provided that the transistor S-parameters are known for each of the bias points. View full abstract»

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  • Technique for antenna array pattern synthesis with controlled broad s

    Publication Year: 1988 , Page(s): 375 - 380
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    The author presents a new technique for synthesising antenna array pattern with controlled broad s. The approach taken in the paper is to integrate the power response of the array over a spatial region of interest and force it to be less than or equal to a small quantity. The optimal weight vector is obtained by minimising the weight vector norm subject to a linear and a quadratic constraint. Numerical techniques based on matrix factorisation are proposed to reduce the computational complexity. Subsequently, a set of linear constraints, also known as eigenvector constraints, are used to approximate the effect of the quadratic constraint in order to maintain a broad over the spatial region of interest. This set of eigenvectors can be viewed as an efficient representation of array signals of specified angular occupancy. View full abstract»

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  • Solution of the resonant frequencies of a cavity resonator by boundary element method (BEM)

    Publication Year: 1988 , Page(s): 361 - 365
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    A three-dimensional vector boundary integral equation suitable for the cavity resonator problem is first given and then discretised resulting in a generalised eigenvalue equation with resonant frequencies as its eigenvalues. The method is applicable to an arbitrarily shaped cavity and the numerical computation is easy to carry out. To demonstrate the accuracy and the feasibility of the method, several numerical examples are presented. View full abstract»

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  • Extension of open resonator measurement technique to achieve fast detailed results over wide bandwidth (8-12 GHz)

    Publication Year: 1988 , Page(s): 431 - 434
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    A large microwave open resonator is operated over a wide bandwidth requiring the application of a microcomputer. The design of a resonator system which achieves the wide bandwidth operation is described. Illustrative applications which demonstrate the scope of the technique are given for the measurement of extinction cross-sections of resonant scattering objects, where considerable detail in behaviour occurs. View full abstract»

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  • Shaped patterns from a continuous planar aperture distribution

    Publication Year: 1988 , Page(s): 366 - 370
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    A pattern synthesis procedure is developed for a planar aperture with a circular boundary. A phi -symmetric continuous distribution is assumed and required to produce a flat-topped beam with controlled ripple, surrounded by ring side lobes of controlled height. With M filled-in s in the shaped region, there are 2M solutions for the aperture distribution. Sampling can yield the excitation of a circular grid planar array. Linear stretching extends the results of an elliptical boundary. View full abstract»

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  • Design aspects and tolerances in array fed contour beam antennas of INTELSAT VI type

    Publication Year: 1988 , Page(s): 408 - 413
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    Using an accurate mutual coupling array analysis technique, a theoretical study of the design aspects of an array fed contour beam reflector antenna of the INTELSAT VI type is made. Emphasis is given to the determination of allowable tolerances on the antenna and beam forming network design parameters, whilst remaining within the main performance constraints of the antenna system. Both single mode and dual mode horn element arrays are considered and their relative merits compared. View full abstract»

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  • Synthesis of sum and difference patterns for two-section monopulse arrays

    Publication Year: 1988 , Page(s): 371 - 374
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    A quadratic programming method is described for studying simultaneous sum and difference synthesis compromises, and establishing performance bounds, under the restriction of a two-section array feed network. A composite objective function is minimised, subject to a union of separate sets of sidelobe constraints, for the sum and difference modes of operation, to avoid a conflicting constraint set. Examples are given to illustrate the principal features of the method. View full abstract»

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  • Available time statistics of rain attenuation on Earth-space path

    Publication Year: 1988 , Page(s): 387 - 390
    Cited by:  Patents (101)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    Rain attenuation data at 19.5 GHz, obtained in a Japanese satellite wave propagation experiment at a measuring rate of 1 sample per second, are analysed. Short term duration statistics of attenuation and statistics of attenuation occurring in available periods, defined in CCITT are derived. In deriving the attenuation statistics during available periods, the total period is divided into periods of available and unavailable times, for several attenuation threshold levels in accordance with the CCITT definition. View full abstract»

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  • Array synthesis with excitation constraints

    Publication Year: 1988 , Page(s): 400 - 407
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (588 KB)  

    The authors present an efficient and flexible method for the optimal synthesis of a shaped beam linear array. This method is capable of dealing with unconstrained as well as constrained synthesis problems. It is based on an iterative process, whose convergence depends on a proper choice of the first approximation. This choice is discussed in detail, and some examples are presented which show the effectiveness of the method in finding the optimal array for a given power pattern. View full abstract»

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  • Improving performance of monopulse phased array in direction finding

    Publication Year: 1988 , Page(s): 391 - 394
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    It is shown that by using Chebyshev weights for the sum pattern while forcing the difference pattern to have the same s except for one pair next to the main beam, the performance of a monopulse phased array in direction finding is improved in the sense that the angular accuracy is less affected by the measurement errors of the sum and difference signal power and the sidelobe levels of both the sum and difference patterns are reduced. View full abstract»

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  • Inexpensive multi-mode satellite tracking feed antenna

    Publication Year: 1988 , Page(s): 381 - 386
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    A design of an inexpensive multi-mode tracking feed antenna, for a circularly polarised signal is described. It uses the TE11 and TM01 modes, in a smooth circular waveguide, to obtain the sum and difference patterns. The higher order mode, TM01 generated within the feed is separated from the dominant mode, TE11 by using the resonant mode filter printed on a thin dielectric material. The design of the resonant mode filter is described in some detail. The use of a printed resonant ring with a dual mode horn makes the design particularly inexpensive. Sum and difference patterns with both the dual mode and the corrugated horn are presented for comparison. View full abstract»

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  • Simple expressions for mutual impedances (dipoles and microstrip elements)

    Publication Year: 1988 , Page(s): 395 - 399
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    A method of evaluating mutual impedances between thin dipoles is presented. They may be free or printed ones. It involves an asymptotic expansion of a bidimensional Fourier integral. Very simple algebraic expressions are derived, which are convenient for hand calculations. The numerical results are more accurate than previously. The technique is extended to include the presence of an infinite ground plane. Then, using the stationary phase method, simple coupling equations are derived for microstrip elements. View full abstract»

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